In order to maximize the capacity of various rotary electric machines as, for example, generators, it is desirable to provide liquid cooling for various components such as windings. In many instances, this does not pose a particular problem. However, in the case of rotary electric machines having rotor windings requiring cooling, a problem may occur in view of the fact that the coolant, frequently oil, seldom is totally free from entrained gases such as air, and the further fact that the coolant passages are displaced from the rotational axis of the rotor.
As a consequence, during operation of the machine, the more dense oil tends to collect in the high centrifugal force field spaced from the rotational axis of the rotor while the less dense air collects in the low centrifugal force area surrounding the rotational axis of the rotor.
Since the coolant is typically introduced into the rotor by a rotary coupling located coaxial with the axis of rotation of the rotor, the air bubble located on the axis of rotation may impede or halt proper flow of the coolant to the coolant passages displaced therefrom with the undesirable result of winding overheating.
The present invention is directed to overcoming one or more of the above problems.